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I got a Raspberry Pi 3 B+ with 2.5A power supply that came with it. I've connected a VGA monitor (via an HDMI-VGA adapter) and keyboard to it, and connected it to the WiFi.

From the beginning, the screen has been going blank erratically. Usually for short but frequent periods. I thought it was the HDMI-VGA adapter or the VGA cable, but I've connected them to my laptop and its experiencing no issues.

I've just noticed right now, that the times the screen goes blank correspond with WiFi activity. If I install packages, the screen will go blank while the download is in progress. If I ping from the RPi, it will go blank until I kill ping with Ctrl-C. If I connect via ssh to it, the screen will go blank while I'm typing from the remote ssh client or the server is responding. I've disconnected the WiFi, and connected the RPi by ethernet, and the issue is gone...

I'm using Arch Linux ARM with no X server (just the linux consoles (e.g. tty1)).

Is this an issue with lack of power? Or is the wifi interfering with the adapter's electronics due to lack of EM shielding or something?

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    You could try increasing config_hdmi_boost (see raspberrypi.org/documentation/configuration/config-txt/video.md) – Dirk Nov 7 '18 at 8:15
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    @Dirk That worked. I set it to 7 as recommended in the link you provided. Can you re-post your comment as an answer, so I can accept it? – JoL Nov 8 '18 at 6:32
  • Remember to accept @Dirk 's answer :) ! – Manchineel Nov 8 '18 at 14:00
  • @Manchineel Of course. :) I was just sleeping. – JoL Nov 8 '18 at 14:39
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I think the most likely problem is HDMI signal strength.

Try setting/increasing config_hdmi_boost in /boot/config.txt

See video options in config.txt for more detailed information. The document recommends 7 as a starting point for HDMI problems:

config_hdmi_boost=7

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